dsync error: Received unexpected input d != N

[David Mandelberg]

Hi,

I'm trying to set up replication with dsync, and I'm getting errors like 
this:

dsync-local(david at mandelberg.org)<...>: Error: dsync(...): Received 
unexpected input d != N

I tried the `doveadm -D sync` command from 
https://doc.dovecot.org/configuration_manual/replication/#administration 
and its output looked like:

...
dsync-local(david at mandelberg.org)<...>: Debug: brain M: Locking done by 
remote (local hostname=..., remote hostname=...)
dsync-local(david at mandelberg.org)<...>: Debug: brain M: Local mailbox 
tree: ...
[line above repeated many times for different mailboxes]
dsync-local(david at mandelberg.org)<...>: Error: dsync(...): Received 
unexpected input d != N
dsync-local(david at mandelberg.org)<...>: Error: dsync(...): Received 
unexpected input d != N
dsync-local(david at mandelberg.org)<...>: Debug: auth-master: conn 
unix:/run/dovecot/auth-userdb (pid=47097,uid=0): Disconnected: 
Connection closed (fd=8)

I'm a bit stuck. Does anybody have any ideas what's going on? The output 
of `doveconf -n` is attached.
-------------- next part --------------
# 2.3.13 (89f716dc2): /etc/dovecot/dovecot.conf
# Pigeonhole version 0.5.13 (cdd19fe3)
# OS: Linux 5.10.0-9-amd64 x86_64 Debian 11.1 ext4
# Hostname: mail-storage-bbf78862.virgo.mandelberg.org
auth_username_chars = +-.0123456789 at ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
dsync_remote_cmd = nc.openbsd -U /run/dovecot/dovecot-replication-client
lda_mailbox_autosubscribe = yes
mail_gid = vmail
mail_home = /var/cache/mail/%{domain}/%{username}/dovecot-home
mail_location = maildir:/var/local/mail/persistent/mail/%{domain}/%{username}/Maildir
mail_plugins = listescape notify replication
mail_uid = vmail
namespace inbox {
  inbox = yes
  location = 
  mailbox Archive {
    special_use = \Archive
  }
  mailbox Drafts {
    special_use = \Drafts
  }
  mailbox Junk {
    special_use = \Junk
  }
  mailbox Sent {
    special_use = \Sent
  }
  mailbox Trash {
    special_use = \Trash
  }
  prefix = 
  separator = /
}
passdb {
  args = /etc/dovecot/conf.d/10-passwd.passdb
  driver = passwd-file
}
plugin {
  mail_replica = remoteprefix:foo at mail-storage-acadbae1.fornax.mandelberg.org
  sieve = file:/usr/local/etc/mail/%{domain}/%{username}/sieve;active=/var/cache/mail/%{domain}/%{username}/active.sieve;bindir=/var/cache/mail/%{domain}/%{username}/sieve
  sieve_before = file:/etc/dovecot/sieve-before
  sieve_filter_bin_dir = /etc/dovecot/sieve-filter-bin
  sieve_filter_exec_timeout = 540s
  sieve_global_extensions = +vnd.dovecot.filter
  sieve_plugins = sieve_extprograms
  sieve_user_log = /var/local/mail/persistent/mail/%{domain}/%{username}/sieve.log
}
postmaster_address = postmaster@%{hostname}
protocols = " imap lmtp"
service aggregator {
  fifo_listener replication-notify-fifo {
    user = vmail
  }
  unix_listener replication-notify {
    user = vmail
  }
}
service auth-worker {
  user = $default_internal_user
}
service auth {
  unix_listener auth-userdb {
    group = vmail
    mode = 0660
  }
}
service imap-login {
  inet_listener imaps {
    port = 993
    ssl = yes
  }
}
service lmtp {
  unix_listener lmtp {
    group = stunnel4
    mode = 0660
  }
  user = vmail
}
service replicator {
  process_min_avail = 1
  unix_listener replicator-doveadm {
    mode = 0600
    user = vmail
  }
}
service stats {
  unix_listener stats-writer {
    mode = 0666
  }
}
ssl = required
ssl_cert = </etc/letsencrypt/live/mail-storage-general.private.mandelberg.org/fullchain.pem
ssl_cipher_list = HIGH:!kRSA:!eNULL:!aNULL:@SECLEVEL=2:@STRENGTH
ssl_key = # hidden, use -P to show it
ssl_min_protocol = TLSv1.2
userdb {
  args = /etc/dovecot/conf.d/10-passwd.userdb
  driver = passwd-file
}
protocol lmtp {
  mail_plugins = listescape notify replication sieve
}
local_name mail-storage-general.private.mandelberg.org {
  ssl_cert = </etc/letsencrypt/live/mail-storage-general.private.mandelberg.org/fullchain.pem
  ssl_key = # hidden, use -P to show it
}
local_name mail-storage-strict.private.mandelberg.org {
  ssl_cert = </usr/local/etc/x509/mail-storage-strict.private.mandelberg.org/cert.pem
  ssl_key = # hidden, use -P to show it
}